Synergistic Activity of the Fe₂O₃/Al₂O₃ Catalyst for Hydrogen Production through Pyrolysis-Catalytic Decomposition of Plastics

Plastic recycling through thermochemical conversion forthe productionof fuels and chemicals is a promising way for simultaneous waste processingand utilization. In the current study, high-density polyethylene (HDPE)was subjected to pyrolysis and then catalytic upgrading to producehydrogen in the presence of a novel Fe2O3/Al2O3 catalyst with a grain boundary. To understandthe catalyst-support interaction as well as the resulting synergisticcatalytic effects, catalytic pyrolysis of HDPE with supported Fe2O3/Al2O3 was compared withthose over Fe2O3, Al2O3, and a cascade combination of both. It was found that the performanceof Fe2O3/Al2O3 was superiorto that of other catalysts in terms of chain cracking and C-C/C-Hbond cleavage. The hydrogen yield with Fe2O3/Al2O3 was 50.53 mmol & BULL;g(plastic) (-1), equivalent to more than 70% of hydrogen inplastic. Besides, alkanes/alkenes ranging from C-2 to C-9 dominated the hydrocarbon products. The analysis of the cycleperformance revealed that the reduction pathway of Fe2O3/Al2O3 was different from those of otherFe(2)O(3)-containing catalysts, which was also confirmedby temperature-programmed reduction. To investigate the essentialrole and reaction mechanism with Fe2O3/Al2O3, characterizations of Fe2O3/Al2O3 before and after the reaction were conducted.The grain boundary between Fe2O3 and Al2O3 enhanced the adsorption of gaseous products.More importantly, the catalyst-support interaction to formFeAl(2)O(4) during the pyrolysis reaction, determinedby X-ray photoelectron spectroscopy, was responsible for effectiveproton adsorption and C-H bond cleavage. This study providesan insightful understanding of catalyst transformation during plasticcatalytic pyrolysis for hydrogen production. Light hydrocarbon vapors from PE pyrolysisare upgradedinto high-value hydrogen through in-situ-formed Fe(II)(tetr) from the Al2O3/Fe2O3 catalyst.